In fluid separation apparatuses, there are several types of membrane forms for fluid separation, for example, plane membranes, tubes, hollow fibers, etc. Among them, hollow fibers have a large membrane area for the size of the case, thus the fluid separation apparatuses therefrom can be advantageously made compact and easy to be operated. Today this type of the fluid separation apparatuses are primarily used.
The process for producing fluid separation apparatuses of a hollow fiber type comprises (1) forming a bundle of hollow fibers of a prescribed count, (2) loading the yarn bundle into a cylindrical case, for example, a plastic case, (3) potting the bundle of hollow fibers to both ends of the case with a resin such as polyurethane, (4) exposing fiber openings by cutting both potted ends of the bundle and (5) fixing the product to the headers.
Collection of hollow fibers into a bundle and encasement thereof have been mainly performed manually conventionally, thus the quality of the products tends to vary too widely, and the production efficiency remains low, thus, the development of a new efficient production method has been desired eagerly.
In the production of a bundle of hollow fibers of a prescribed count, the total cross-section of the bundle is generally formed into a flat, round or square shape, depending on the cases, and the cross section of the bundle is required to be almost the same as the inner cross section of the case, and the sizes of the cross section, namely the diameter, if the cross section is round, or the major and minor axes, if elliptical, or the length and width, if rectangular, should be the same as or just a little smaller than those of the case, when a bundle is loaded into the case.
When it satisfies these conditions, the bundle of yarn fibers formed can be readily loaded into the case, but, if not, the shape of its cross-section should be modified.
Heretofore, it has been ordinary that the shape modification of the cross section is mainly performed manually because of the difficulty of the modification of the cross section by an apparatus. In addition, the bundle of hollow fibers which has been modified by hand is usually loaded into the case by hand carefully and slowly. Such handiwork, however, must largely rely on the art of each worker, resulting in fluctuations in the product quality as well as the productivity. The present invention is to resolve these problems.
Moreover, with reference to the production of a fluid separation apparatus of a hollow fiber type such as a hemodialyzer, one of conventional methods for loading a bundle of permselective hollow fibers into the cylindrical case of a fluid separator comprises binding each bundle of hollow fibers with a tape at both ends and pushing one end of the bundle forcibly by hand into the case, or connecting a string through the cylindrical case to one end of the yarn bundle and pulling the other end of the string to introduce the bundle into the case.
In these conventional methods, a skilled worker is required to adjust the form of the fiber bundles by hand for inserting them into the cylindrical case one by one carefully, and such low efficiencies of these operations have been the bottle neck for efficient production of the fluid separation apparatuses of a hollow fiber type with productivity increased. In addition, the friction with the wall surface on the insertion tends to disturb the parallelism of the hollow fibers, and sometimes causes deterioration such as breakage of the hollow fibers, which results in lower productivity of such fluid separators.
Recently, for example, Japanese Patent Laid-open No. 54711/1985 has proposed a method that the bundle of hollow fibers is previously wrapped with a sheet so that one end of the bundle is hidden, while the other exposed, then inserted into one opening of the case from the hidden end and only the sheet is pulled out of the other opening, and Japanese Patent Laid-open No. 86,906/1986 has disclosed a method that the bundle of hollow fibers is previously wrapped with a cylindrical bag to which a string is attached at one end so that the other end of the string contacts one end of the hollow fiber bundle, and loaded into the outer case by introducing the wrapped bundle from the end to which the string is attached into the protection cylinder case and pulling off the cylindrical bag by drawing the string. The preliminary operation to wrap the hollow fiber bundle, however, are very complicated, in particular, the process tends to become complicated, when the bundle is loaded into a cylindrical case by an automated system. Thus, further improvement has been desired.